A. Field of Invention
The present invention relates generally to power transmission mechanisms, and more particularly to a new and improved means for providing a variable speed transmission with reversible power output.
B. Description of Related Art
A number of relatively simple mechanical power transmission devices exist wherein the essential power transfer mechanism involves a friction disc which is rotated by the power source and the spinning disc surface is impacted by a driven wheel that is aligned such that the axis of the driven wheel is parallel to a radius of the friction disc. In such devices, the power output is varied by radially altering the displacement of the driven wheel from the center point of the friction wheel and the point of engagement of the driven wheel and friction disc. Examples of such devices include U.S. Pat. No. 3,818,954 to Price; U.S. Pat. No. 3,631,730 to Hadler; U.S. Pat. No. 4,498,552 to Rouse; and U.S. Pat. No. 3,613,814 to Prien. Since the common usage of such devices is to transmit power to wheels to propel mowers or other small vehicles, it would be beneficial if the device was capable of reversing the power output and in particular of reversing power direction without disengaging the power as a required step in the reversing process. In addition, it would be advantageous to utilize the power transmission device to provide a steering function. Steering by means of varying power output to separate wheels requires that the transmission device must be compact and efficiently able to individually alter multiple outputs from a single power source. Of the mentioned devices, the device disclosed in Prien does not appear to reversible, and the Price and Hadler devices require disengagement of power when shifting from a forward speed to reverse. The Price, Rouse and Hadler devices also appear capable of only providing a single power output and are not readily adaptable to separately drive separate wheels at independent speeds, as is necessary to make the variance of power output a means for steering the vehicle utilizing the device as a power transmission. The object of the present invention is to overcome the limitations of the known friction drive mechanisms by providing for the axis of the rotational axis of the power input being parallel to the rotational axis of the power output. It is further desired to provide a power transmission device capable of a smooth and direct transition from forward to reverse speed without the necessity of disengaging the power source with a single control that varies both the speed and the direction of the power output in a continuous manner. Finally, the present invention is designed to overcome the limitations of the cited art of having only a single power output with the effect that a vehicle utilizing the present invention may be steered by independently varying the speed and direction of rotation of two drive wheels.